SpaceX and Boeing have been working on their space taxi programs for almost four years, with the aim of transporting astronauts to and from the space station for NASA.

"For the first time since 2011, we are on the brink of launching American astronauts on American rockets from American soil", NASA Administrator Jim Bridenstine said Friday, standing in front of a giant American flag at Johnson Space Center in Houston.

The chosen astronauts will be the first to conduct flight tests and missions on the Boeing Starliner and Space X crew dragon.

The two missions from SpaceX and Boeing will be the first to launch from the USA since NASA's last space shuttle launched, in 2011.

The unpiloted supply ship launched from Cape Canaveral on June 29 aboard a Falcon 9 rocket, and it reached the space station July 2.

A commercial Dragon cargo craft launched June 29 departed the International Space Station and returned to Earth on Friday with almost two tons of cargo and research samples. (BA) to the punch when it comes to flying astronauts to the International Space Station. "It will be thrilling to see our astronauts lift off from American soil, and we can't wait to see them aboard the International Space Station".

Prior to their maiden crewed missions, both Boeing and SpaceX plan uncrewed test flights in late 2018 or early 2019. He flew on two flights of the space shuttle including the final mission, Atlantis's STS-135.

The first SpaceX Crew Dragon flight to the space station will include NASA astronaut and Navy test pilot Victor Glover, who has logged more than 3,000 hours flying 40 different aircraft and NASA astronaut Mike Hopkins, who has logged 166 days in space so far. Boeing's and SpaceX's commercial spacecraft may also open the space station - and more broadly, Earth orbit - to more privately-funded visitors and spaceflight participants from countries that do not have their own domestic crewed spacecraft and rockets.

Behnken, Boe, Hurley and Williams were named in 2015 as Nasa's "commercial crew cadre" and have been working with Boeing and SpaceX on the development of the spacecraft and the simulators that will be used to train astronauts to fly.

The astronauts assigned to the Starliner's first mission are Sunita Williams, who retired as a Navy captain, and Cmdr.

Boe is a former shuttle pilot; Mann will be making her first trip into space.

Additional crew members will be assigned by NASA's worldwide partners at a later date. This will be his first spaceflight. SpaceX's manned test flight will feature two NASA astronauts.

NASA's continuous presence on the space station for nearly 18 years has enabled technology demonstrations and research in biology and biotechnology, Earth and space science, human health, physical sciences. Williams previously logged 321 days in orbit on two stays aboard the space station, most recently returning to the Earth in 2012. The launch window for the mission opens at 3:48 a.m EDT on August 11, 2018.